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Quantitative morphometric analyses of iliac crest biopsies from 20 epileptic patients receiving chronic anticonvulsant therapy have been performed before and after 4-8 months of vitamin D2 treatment with 9 000 U per day. Biochemical quantities, including serum 25-hydroxycholecalciferol (25-HCC) and serum parathyroid hormone (iPTH), were measured. The anticonvulsant osteomalacia found in the initial bone biopsies was characterized by an increased amount of ummineralized bone, an increased bone resorption and, contrary to vitamin D deficiency, an increased bone mineralization and bone formation. Bone resorption and bone formation were probably equally increased since the amount of cancellous bone was normal. Except for a slight increase in osteoidcovered surfaces and osteoclastic resorption surfaces, the bone changes were normalized after vitamin D2 treatment, leading to a mean serum level of 25-HCC 2.4 times above normal. Serum iPTH was normal before and unchanged during D2 therapy. The urinary calcium excretion remained decreased. The investigation characterizes anticonvulsant osteomalacia as a specific bone disease different from that of vitamin D deects of vitamin D metabolites on receptor cells.

Roentgendensitometric measurements were correlated with quantitative histological analysis of cortical and cancellous bone from a standard anatomical site on the iliac crest. The point-count method was used to quantitate spongy bone in 8 mu thick sections. Measurements of the thickness of the cortices were made with a micrometric eyepiece. The reproducibility of the method for the roentgendensitometric analysis was found to be about 1 per cent of the mean for all variables. The correlation between roentgendensitometric and histological analysis was found to be low (r=0.44) and could be ascribed mainly to variation in the thickness of the cortices which again was only slightly correlated with the percentage of spongy bone (r=0.39). Both the determination of the amount of bone mineral and of bone by quantitative histometric analysis are required for diagnosis of skeletal system disorders.